Valve Lapping Techniques - Need Some Input

[rmaynard 14,932]

I am in the process of rebuilding the K181 engine from my 857. The engine ran strong, but it was a heavy smoker. So I am at the point of the rebuild where I am attempting to lap in my new valves. Here is my problem. The valves that I am using are genuine Kohler, and they are flat on the tops with no dimples. The surface is also semi-rough, as if bead blasted. Problem is, a suction cup-type valve tool will not stick.

 

So here is my question for all you rebuilders. Does anyone have a method of attaching something to the surface so that I can use a low speed drill to do my lapping?

[WH nut 553]

Hot glue gun, and no drill. You need to lap them in with a back and forth motion

Edited January 12, 2014 by WH nut

[rmaynard 14,932]

Tried hot glue. Doesn't stick.

[WH nut 553]

Well that sucks

[rmaynard 14,932]

I did read somewhere of taking an old valve and epoxying it upside down onto the new valve. Seems like a lot of work getting the epoxy off afterwards. However, if hot glue won't stick, I'm afraid epoxy won't either.

[WH nut 553]

I don't think I like the epoxy idea. was the valve good and clean when you tried glue?

[dclarke 4,011]

Would Velcro work, Bob? Not sure you could get that to stick either.

[rmaynard 14,932]

Yup, I cleaned it with brake cleaner, then 99% isopropol alcohol.

[rmaynard 14,932]

I have some Velcro and it has a pretty good stick'um on the back. I'll have to give that a try. Thanks!

[Don1977 604]

Have you tried double stick tape. It's a real pain to remove, might need gas or paint thinner to get the glue off.

[KC9KAS 4,741]

As stated above....Lap the valves with a back & forth motion.

You can gradually rotate the valve while lapping back & forth, but you don't want to just lap in a circular motion.

[sorekiwi 761]

I lick the the suction cup and stick it onto the valve.  Valve grinding paste does taste bad.

 

I once tried one of those valve lapping tools that auto reverse with a crank handle (like an old style hand drill or an egg beater).  Persevered with it for about 30 seconds, and went back to the plain old sucker.

[Martin 2,130]

I'm with Mike on the licking the suction cup, that paste isn't real tasty in a good way. (not as good as vegemite anyway)

 

could you smooth the valve head some amount by running it over some 220 or similar on a flat surface? just a little circular motion to level out some of that surface 'roughness'?

 

ive had a few valves that were 'rough' like you described and i persevered with the suction cup. some worked without smoothing some didn't. get that suction cup as wet as possible and it helped a little. air will still escape but might give you a few rotations and work the paste enough to break the hold it has on the valve and seat.

Edited January 12, 2014 by Martin

[TT-(Moderator) 1,128]

I've used all sorts of methods including wrapping a piece of string around the stem (think snowthrower cable spool) to a strong magnet on the valve face.

 

Were the seats ground?

New (or properly ground) valves in freshly cut seats shouldn't require much more than a twist or two to check the contact area.

Most of the time I just use a Sharpie to "paint" the seat face and spin the valve against the seat to mark the contact area.

[Anglo Traction 759]

Bees Wax! . Clean the rough area first,  Melt it onto the Valve head and let it flow flat and smooth to cool. 

You can scrape it if to leave it in the pits and uneven areas.

I always only do them by hand, I get more control that way, but you can try it with a drill if you wish. Wet the Sucker with water.

Clean off after using Mineral Spirits.

[rmaynard 14,932]

Were the seats ground?

New (or properly ground) valves in freshly cut seats shouldn't require much more than a twist or two to check the contact area...

The seat were not ground. They were in good shape, but since the decision was made to install new valves, I wanted to lap them for good measure.

 

I have since used the Velcro method suggested by Denny. The adhesive on the Velcro was amazing. It was actually hard to get back off again. I put the opposite side on an old valve that I cut the stem down a bit and stuck in the chuck of my reversing electric screw driver. I did a couple of revolutions in one direction, then pushed the reverse button for a couple, and so on. Got a good lap on the valves and seats.

 

Thanks for all the answers and suggestions. I now have a new tool in the engine rebuild drawer.

[woodchuckfarmer 333]

Try 3m weather strip adhesive. It sticks to most anything.

[dclarke 4,011]

Glad that worked, Bob. Now if I can just remember it if I run into the same thing.

[Fordiesel69 226]

Purchase a suction cup tool from a store other than harbor freight.  I have an old one from napa and it will work on dirty valves.  They key is lots of spit on the suction cup.  Use very little pressure downwards on the valve, let the compoud do the cutting for you, and pick up the valve often to redistribute the compound.

 

FYI, a dry suction cup tool will almost never work even when brand new.

[rmaynard 14,932]

Hey, I was a kid of the 1950's. We had bow and arrows with suction cups that we shot at everything while playing cowboys and Indians. I probably left more spit behind than a Rottweiler. My mother always yelled at me for leaving spit rings on the TV screen.

 

My valve tool is from Cornwell Tools, not Harbor Freight. It works well on most other valves, especially those with a fairly smooth surface, but no matter how much spit I apply, it will always slip off of these new Kohler valves.

[BPC23 18]

A couple weeks ago I successfully used a pair of valves and hot glue.  The first two times my father-in-law and I applied hot glue to one valve, pressed the two together, it didn't stick very well.  We tried again using more glue than we did before.  Still didn't stick.  So we tried one more time, covering just about the entire valve head with hot glue and it worked.  We were able to lap both valves by hand.  We then carefully separated the valves using a small flat-tip screwdriver like a chisel to "shear" them apart.

 

I didn't test the theory, but I suspect the hot glue didn't initially stick to the valves because: 1) they had a little bit of oil residue on the surface; 2) they were too cold.

 

Brian

Edited January 16, 2014 by BPC23